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From: Jim Thompson <jim@netgate.com>
Date: Thu, 25 May 2006 16:32:46 -1000
To: "James Mansion" <james@wgold.demon.co.uk>
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Cc: Alexander Leidinger <Alexander@Leidinger.net>,
	Poul-Henning Kamp <phk@phk.freebsd.dk>,
	Andrew Atrens <atrens@nortel.com>, small@freebsd.org, current@freebsd.org
Subject: Re: FreeBSD's embedded agenda
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On May 25, 2006, at 1:03 PM, James Mansion wrote:

>> It would support wear-levelling
>
> I think this might in practice be a red-herring.

If you're assuming CF, possibly.

If you're assuming a lower level flash interface, no.

> If you could convince the system to set aside an amount
> of RAM for dirty disk buffers and to write them all when
> its filled or on application demand (and in a way that
> preseves integrity like soft updates) so that for any
> given flush each sector is written at most once, then
> you can run for years for most CF cards and most practical
> usage patterns that don't really demand a hard disk.

embedded systems are constrained in memory size, too.

> Assume you have cron drive a flush once an hour and
> consider how long until a sector dies, even if the drive
> itself does no wear levelling at all (and I believe some
> do it internally).

internal wear-leveling
CF: yes
otherwise: not typically.

Might want to re-think your argument in terms of a system with 32MB  
of ram
and 4MB of NAND or NOR flash.